Venous Anatomy of the Central Nervous System.

Comprehensive understanding of venous anatomy is a key factor in the approach to a multitude of conditions. Moreover, the venous system has become the center of attention as a new frontier for treatment of diseases such as idiopathic intracranial hypertension (IIH), arteriovenous malformation (AVM), pulsatile tinnitus, hydrocephalus, and cerebrospinal fluid (CSF) venous fistulas. Its knowledge is ever more an essential requirement of the modern brain physician. In this article, the authors explore the descriptive and functional anatomy of the venous system of the CNS in 5 subsections: embryology, dural sinuses, cortical veins, deep veins, and spinal veins.

Venous-plexus-associated lymphoid hubs support meningeal humoral immunity.

There is increasing interest in how immune cells in the meninges-the membranes that surround the brain and spinal cord-contribute to homeostasis and disease in the central nervous system1,2. The outer layer of the meninges, the dura mater, has recently been described to contain both innate and adaptive immune cells, and functions as a site for B cell development3-6. Here we identify organized lymphoid structures that protect fenestrated vasculature in the dura mater. The most elaborate of these dural-associated lymphoid tissues (DALT) surrounded the rostral-rhinal confluence of the sinuses and included lymphatic vessels. We termed this structure, which interfaces with the skull bone marrow and a comparable venous plexus at the skull base, the rostral-rhinal venolymphatic hub. Immune aggregates were present in DALT during homeostasis and expanded with age or after challenge with systemic or nasal antigens. DALT contain germinal centre B cells and support the generation of somatically mutated, antibody-producing cells in response to a nasal pathogen challenge. Inhibition of lymphocyte entry into the rostral-rhinal hub at the time of nasal viral challenge abrogated the generation of germinal centre B cells and class-switched plasma cells, as did perturbation of B-T cell interactions. These data demonstrate a lymphoid structure around vasculature in the dura mater that can sample antigens and rapidly support humoral immune responses after local pathogen challenge.

Piezo1 Is a Mechanosensor Channel in Central Nervous System Capillaries.

Capillaries are equipped to sense neurovascular coupling agents released onto the outer wall of a capillary, translating these external signals into electrical/Ca2+ changes that play a crucial role in blood flow regulation and ensuring that neuronal demands are met. However, control mechanisms attributable to forces imposed onto the lumen are less clear. Here, we show that Piezo1 channels act as mechanosensors in central nervous system capillaries. Electrophysiological analyses confirmed expression and function of Piezo1 channels in brain cortical and retinal capillaries. Activation of Piezo1 channels evoked currents that were sensitive to endothelial cell-specific Piezo1 deletion. Using genetically encoded Ca2+ indicator mice and an ex vivo pressurized retina preparation, we found that activation of Piezo1 channels by mechanical forces triggered Ca2+ signals in capillary endothelial cells. Collectively, these findings indicate that Piezo1 channels are capillary mechanosensors that initiate crucial Ca2+ signals and could, therefore, have a profound impact on central nervous system blood flow control.

CNS endothelial derived extracellular vesicles are biomarkers of active disease in multiple sclerosis.

BACKGROUND: Multiple sclerosis (MS) is a complex, heterogenous disease characterized by inflammation, demyelination, and blood-brain barrier (BBB) permeability. Currently, active disease is determined by physician confirmed relapse or detection of contrast enhancing lesions via MRI indicative of BBB permeability. However, clinical confirmation of active disease can be cumbersome. As such, disease monitoring in MS could benefit from identification of an easily accessible biomarker of active disease. We believe extracellular vesicles (EV) isolated from plasma are excellent candidates to fulfill this need. Because of the critical role BBB permeability plays in MS pathogenesis and identification of active disease, we sought to identify EV originating from central nervous system (CNS) endothelial as biomarkers of active MS. Because endothelial cells secrete more EV when stimulated or injured, we hypothesized that circulating concentrations of CNS endothelial derived EV will be increased in MS patients with active disease. METHODS: To test this, we developed a novel method to identify EV originating from CNS endothelial cells isolated from patient plasma using flow cytometry. Endothelial derived EV were identified by the absence of lymphocyte or platelet markers CD3 and CD41, respectively, and positive expression of pan-endothelial markers CD31, CD105, or CD144. To determine if endothelial derived EV originated from CNS endothelial cells, EV expressing CD31, CD105, or CD144 were evaluated for expression of the myelin and lymphocyte protein MAL, a protein specifically expressed by CNS endothelial cells compared to endothelial cells of peripheral organs. RESULTS: Quality control experiments indicate that EV detected using our flow cytometry method are 0.2 to 1 micron in size. Flow cytometry analysis of EV isolated from 20 healthy controls, 16 relapsing-remitting MS (RRMS) patients with active disease not receiving disease modifying therapy, 14 RRMS patients with stable disease not receiving disease modifying therapy, 17 relapsing-RRMS patients with stable disease receiving natalizumab, and 14 RRMS patients with stable disease receiving ocrelizumab revealed a significant increase in the plasma concentration of CNS endothelial derived EV in patients with active disease compared to all other groups (p = 0.001). CONCLUSIONS: For the first time, we have identified a method to identify CNS endothelial derived EV in circulation from human blood samples. Results from our pilot study indicate that increased levels of CNS endothelial derived EV may be a biomarker of BBB permeability and active disease in MS.

Application and advantages of zebrafish model in the study of neurovascular unit.

The concept of "Neurovascular Unit" (NVU) was put forward, so that the research goal of Central Nervous System (CNS) diseases gradually transitioned from a single neuron to the structural and functional integrity of the NVU. Zebrafish has the advantages of high homology with human genes, strong reproductive capacity and visualization of neural circuits, so it has become an emerging model organism for NVU research and has been applied to a variety of CNS diseases. Based on CNKI (https://www.cnki.net/) and PubMed (https://pubmed.ncbi.nlm.nih.gov/about/) databases, the author of this article sorted out the relevant literature, analyzed the construction of a zebrafish model of various CNS diseases，and the use of diagrams showed the application of zebrafish in the NVU, revealed its relationship, which would provide new methods and references for the treatment and research of CNS diseases.

A human cell type similar to murine central nervous system perivascular fibroblasts.

The brain vasculature has several specific features, one of them being the blood-brain barrier (BBB), which supports and protects the brain by allowing for the passage of oxygen and nutrients, while at the same time preventing passage of pathogens and toxins. The BBB also prevents efficient delivery of drugs to the brain, e.g. for treatment of brain tumors. In the murine brain, perivascular fibroblasts were recently identified as a novel potential constituent of the BBB. Here we present the existence of human cells that could be the equivalent to the murine brain perivascular fibroblasts. Using RNA sequencing, we show a similar transcriptomic profile of cultured human brain cells and murine perivascular fibroblasts. These data open up a window for new hypotheses on cell types involved in human CNS diseases.

Conventional and advanced MRI evaluation of brain vascular malformations.

Vascular malformations (VMs) of the central nervous system (CNS) include a wide range of pathological conditions related to intra and extracranial vessel abnormalities. Although some VMs show typical neuroimaging features, other VMs share and overlap pathological and neuroimaging features that hinder an accurate differentiation between them. Hence, it is not uncommon to misclassify different types of VMs under the general heading of arteriovenous malformations. Thorough knowledge of the imaging findings of each type of VM is mandatory to avoid these inaccuracies. Conventional MRI sequences, including MR angiography, have allowed the evaluation of CNS VMs without using ionizing radiation. Newer MRI techniques, such as susceptibility-weighted imaging, black blood sequences, arterial spin labeling, and 4D flow imaging, have an added value of providing physiopathological data in real time regarding the hemodynamics of VMs. Beyond MR images, new insights using 3D printed models are being incorporated as part of the armamentarium for a noninvasive evaluation of VMs. In this paper, we briefly review the pathophysiology of CNS VMs, focusing on the MRI findings that may be helpful to differentiate them. We discuss the role of each conventional and advanced MRI sequence for VMs assessment and provide some insights about the value of structured reports of 3D printing to evaluate VMs.

EphA2, vascular endothelial growth factor, and vascular endothelial growth factor correlate with adverse outcomes and poor survival in patients with glioma.

PURPOSE: To assess expression levels of Ephrin type-A receptor 2 (EphA2), vascular endothelial growth factor (VEGF), and von Willebrand factor (vWF), and assess their potentials as prognostic biomarkers to predict the risk of poor survival in patients with primary lower grade glioma. METHOD: The study included75 patients with histopathologically confirmed primary glioma (World Health Organization Grade IV). All patients underwent combined surgery and postoperative radiotherapy for the management of primary glioma. Immuno-histochemical analysis was performed to evaluate expression levels ofEphA2 and VEGF. Evaluation of tumor microvessel density was also performed at angiogenesis hot spots due to tumor growth. Main outcomes of the study were the prognostic efficiencies of EphA2, VEGF, and vWF in primary low-grade glioma, as well as whether their expression levels were associated with cancer progression. RESULTS: Of the patients with glioma, 67% had very strong expression of EphA2. Overall survival was inversely correlated with the expression of EphA2. Regarding VEGF expression, 38 patients (51%) had strong expression, 29 patients (39%) had weak expression, and 8 patients (11%) had no expression. Strong VEGF expression was associated with poor prognosis and poor survival. CONCLUSION: EphA2, VEGF, and vWF could be considered prognostic markers for assessment of primary glioma.

Endothelial-Tumor Cell Interaction in Brain and CNS Malignancies.

Glioblastoma and other brain or CNS malignancies (like neuroblastoma and medulloblastoma) are difficult to treat and are characterized by excessive vascularization that favors further tumor growth. Since the mean overall survival of these types of diseases is low, the finding of new therapeutic approaches is imperative. In this review, we discuss the importance of the interaction between the endothelium and the tumor cells in brain and CNS malignancies. The different mechanisms of formation of new vessels that supply the tumor with nutrients are discussed. We also describe how the tumor cells (TC) alter the endothelial cell (EC) physiology in a way that favors tumorigenesis. In particular, mechanisms of EC-TC interaction are described such as (a) communication using secreted growth factors (i.e., VEGF, TGF-ß), (b) intercellular communication through gap junctions (i.e., Cx43), and (c) indirect interaction via intermediate cell types (pericytes, astrocytes, neurons, and immune cells). At the signaling level, we outline the role of important mediators, like the gasotransmitter nitric oxide and different types of reactive oxygen species and the systems producing them. Finally, we briefly discuss the current antiangiogenic therapies used against brain and CNS tumors and the potential of new pharmacological interventions that target the EC-TC interaction.

Three-Dimensional Imaging of the Vertebral Lymphatic Vasculature and Drainage using iDISCO+ and Light Sheet Fluorescence Microscopy.

The lymphatic system associated with the central nervous system (CNS) includes the lymphatic vasculature that spins around the brain, the spinal cord, and its associated LNs. The CNS-associated lymphatic system is involved in the drainage of CSF macromolecules and meningeal immune cells toward CNS-draining LNs, thereby regulating waste clearance and immune surveillance within CNS tissues. Presented is a novel approach to obtain three-dimensional (3D) and cellular resolution images of CNS-associated lymphatics while preserving the integrity of their circuits within surrounding tissues. The iDISCO+ protocol is used to immunolabel lymphatic vessels in decalcified and cleared whole mount preparations of the vertebral column that are subsequently imaged with light sheet fluorescence microscopy (LSFM). The technique reveals the 3D structure of the lymphatic network connecting the meningeal and epidural spaces around the spinal cord to extravertebral lymphatic vessels. Provided are 3D images of the drainage circuits of molecular tracers previously injected into either the CSF via the cisterna magna or the thoracolumbar spinal parenchyma. The iDISCO+/LSFM approach brings unprecedented opportunities to explore the structure and function of the CNS-associated lymphatic system in neurovascular biology, neuroimmunology, brain and vertebral cancer, or vertebral bone and joint biology.

Reliable Isolation of Central Nervous System Microvessels Across Five Vertebrate Groups.

Isolation of microvessels from the central nervous system (CNS) is commonly performed by combining cortical tissue from multiple animals, most often rodents. This approach limits the interrogation of blood-brain barrier (BBB) properties to the cortex and does not allow for individual comparison. This project focuses on the development of an isolation method that allows for the comparison of the neurovascular unit (NVU) from multiple CNS regions: cortex, cerebellum, optic lobe, hypothalamus, pituitary, brainstem, and spinal cord. Moreover, this protocol, originally developed for murine samples, was successfully adapted for use on CNS tissues from small and large vertebrate species from which we are also able to isolate microvessels from brain hemisphere white matter. This method, when paired with immunolabeling, allows for quantitation of protein expression and statistical comparison between individuals, tissue type, or treatment. We proved this applicability by evaluating changes in protein expression during experimental autoimmune encephalomyelitis (EAE), a murine model of a neuroinflammatory disease, multiple sclerosis. Additionally, microvessels isolated by this method could be used for downstream applications like qPCR, RNA-seq, and Western blot, among others. Even though this is not the first attempt to isolate CNS microvessels without the use of ultracentrifugation or enzymatic dissociation, it is unique in its adeptness for the comparison of single individuals and multiple CNS regions. Therefore, it allows for investigation of a range of differences that may otherwise remain obscure: CNS portions (cortex, cerebellum, optic lobe, brainstem, hypothalamus, pituitary, and spinal cord), CNS tissue type (gray or white matter), individuals, experimental treatment groups, and species.

Chronic cerebrospinal venous insufficiency and menière's disease: Interventional versus medical therapy.

OBJECTIVES/HYPOTHESIS: To evaluate the incidence of chronic cerebrospinal venous insufficiency in Menière's disease patients and the effect of bilateral percutaneous transluminal angioplasty of the jugular/azygos veins compared to medical therapy. STUDY DESIGN: Prospective case-control study. METHODS: Five hundred fourteen subjects were included in the study, 412 affected by definite Menière's disease, and 102 healthy controls. All patients underwent audiovestibular and vascular examination. Patients with Menière's disease and concomitant cerebrospinal venous insufficiency were divided in two subgroups: patients who underwent vascular intervention with bilateral percutaneous transluminal angioplasty (PTA) of the jugular/azygos veins and patients treated with medical therapy. RESULTS: Chronic cerebrospinal venous insufficiency was diagnosed in 330/412 (80.1%) Menière's disease patients and in 12/102 healthy individuals (11.8%) (P < .001). In the two chronic cerebrospinal venous insufficiency subgroups, a significant difference in Dizziness Handicap Inventory scores was found between patients in the PTA group compared to patients treated with medical therapy (31 ± 8.6 vs. 48.1 ± 14.4; P < .001); no significant differences were found for the Tinnitus Handicap Inventory scores (50.8 ± 16.58 vs. 49.6 ± 17.5; P = .23). Subjective evaluation of aural fullness was significantly better in patients in the PTA group (P = .003) as well as pure-tone average, which was significantly different between groups (49.8 ± 16.5 dB in the PTA group vs. 55.8 ± 13 in the medical therapy group; P = .035). CONCLUSIONS: The results of the present study confirm the close relationship between vascular disorders and Menière's disease. The encouraging responses to vascular interventional therapy on Meniére's disease symptoms suggest that this may be a promising path for interpretation and treatment of this complex disease. LEVEL OF EVIDENCE: 2b Laryngoscope, 130: 2040-2046, 2020.

CD8+ T cell-mediated endotheliopathy is a targetable mechanism of neuro-inflammation in Susac syndrome.

Neuroinflammation is often associated with blood-brain-barrier dysfunction, which contributes to neurological tissue damage. Here, we reveal the pathophysiology of Susac syndrome (SuS), an enigmatic neuroinflammatory disease with central nervous system (CNS) endotheliopathy. By investigating immune cells from the blood, cerebrospinal fluid, and CNS of SuS patients, we demonstrate oligoclonal expansion of terminally differentiated activated cytotoxic CD8+ T cells (CTLs). Neuropathological data derived from both SuS patients and a newly-developed transgenic mouse model recapitulating the disease indicate that CTLs adhere to CNS microvessels in distinct areas and polarize granzyme B, which most likely results in the observed endothelial cell injury and microhemorrhages. Blocking T-cell adhesion by anti-α4 integrin-intervention ameliorates the disease in the preclinical model. Similarly, disease severity decreases in four SuS patients treated with natalizumab along with other therapy. Our study identifies CD8+ T-cell-mediated endotheliopathy as a key disease mechanism in SuS and highlights therapeutic opportunities.

A critical role for microglia in maintaining vascular integrity in the hypoxic spinal cord.

Hypoxic preconditioning reduces disease severity in a mouse model of multiple sclerosis (MS), in part by enhancing the barrier properties of spinal cord blood vessels. Because other studies have shown that similar levels of hypoxia transiently increase permeability of central nervous system (CNS) blood vessels, the goal of this study was to define the impact of chronic mild hypoxia (CMH, 8% O2) on the integrity of spinal cord blood vessels and the responses of neighboring glial cells. Using extravascular fibrinogen as a marker of vascular disruption, we found that CMH triggered transient vascular leak in spinal cord blood vessels, particularly in white matter, which was associated with clustering and activation of Mac-1-positive microglia around disrupted vessels. Microglial depletion with the colony stimulating factor-1 receptor (CSF-1R) inhibitor PLX5622, while having no effect under normoxic conditions, profoundly increased vascular leak in both white and gray matter during CMH, and this was associated with disruption of astrocyte-vascular coupling and enhanced loss of tight junction proteins. Microglial repair of leaky blood vessels was blocked by a peptide that inhibits the interaction between fibrinogen and its Mac-1 integrin receptor. These findings highlight an important role for microglia in maintaining vascular integrity in the hypoxic spinal cord and suggest that a fibrinogen-Mac-1 interaction underpins this response. As relative hypoxia is experienced in many situations including high altitude, lung disease, obstructive sleep apnea, and age-related CNS ischemia/hypoxia, our findings have important implications regarding the critical role of microglia in maintaining vascular integrity in the CNS.

Neurovascular Interactions in the Nervous System.

Molecular cross talk between the nervous and vascular systems is necessary to maintain the correct coupling of organ structure and function. Molecular pathways shared by both systems are emerging as major players in the communication of the neuronal compartment with the endothelium. Here we review different aspects of this cross talk and how vessels influence the development and homeostasis of the nervous system. Beyond the classical role of the vasculature as a conduit to deliver oxygen and metabolites needed for the energy-demanding neuronal compartment, vessels emerge as powerful signaling systems that control and instruct a variety of cellular processes during the development of neurons and glia, such as migration, differentiation, and structural connectivity. Moreover, a broad spectrum of mild to severe vascular dysfunctions occur in various pathologies of the nervous system, suggesting that mild structural and functional changes at the neurovascular interface may underlie cognitive decline in many of these pathological conditions.

[The application of hybrid operation suite in the management of cerebral and spinal vascular diseases and intracranial hypervascular tumors].

Objective: To evaluate the effect of hybrid operation suite in the treatment of cerebral and spinal vascular diseases and intracranial hypervascular tumors. Methods: A retrospective study was conducted on 132 patients with various cerebral and spinal vascular diseases and intracranial hypervascular tumors who were treated by hybrid surgery at Department of Neurosurgery, Huashan Hospital from October 2016 to December 2017.There were 70 male and 62 female patients with a mean age of 48.33 years (range: 14-78 years), including 64 cases of intracranial aneurysm (41 complicated aneurysm cases), 28 cases of brain arteriovenous malformation (BAVM), 12 cases of hypervascular tumor, 12 cases of dural arteriovenous fistula (DAVF), 6 cases of carotid artery stenosis, 5 cases of Moyamoya disease, 3 cases of intracranial aneurysm or BAVM combined with tumor, 1 case of scalp arteriovenous fistula and 1 case of critical brain trauma in which a foreign metal stick approached the basal vascular circuit.Abnormalities were found in 16 cases in intraoperative angiography. The clinical data of all patients was collected as a perspective cohort. The success rate of hybrid surgery, intra-operative and post-operative complications, morbidity, mortality, rate of infection, the length of hospital stay were all analyzed to illustrate the effect of hybrid operation mode to traditional surgical pattern. Results: For 64 cases with intracranial aneurysms, the immediate complete occlusion rate was 90.5%, with a mortality of 4.7% and a morbidity of 14.0%. For 28 cases of BAVM and 12 cases of DAVF, all patients achieved total obliteration and favorable social independent outcomes after hybrid surgery, with no complication.For 6 cases of carotid artery stenosis and 5 cases of Moyamoya, intra-operative confirmed good cerebral reperfusion without any new post-operative neurologic deficits. After tumor vessels embolization, 4 out of 12 cases of hypervascular tumor needed intra-operative blood transfusion, and all patients achieved total tumor resection in a single stage. Only one patient with medulla oblongata hemangioblastoma died 6 months after operation due to respiratory deficit related pneumonia. Compared to traditional surgeries, the hybrid operation pattern did not significantly increase the total infection rate, central nervous system infection rate, hospital stay days and post-operative hospital stay days (all P>0.05) while the in-patient cost increased mildly (119 332 yuan vs.98 215 yuan, t=2.38, P=0.02). Conclusions: The operations of complex cerebral and spinal vascular diseases and intracranial hypervascular tumors can be performed in hybrid operation suite safely.This surgical mode can ensure the quality of operation and promote the development of innovative and complicated surgical procedures.

Fluid dynamics of cerebrospinal venous flow in multiple sclerosis.

Stenotic immobile valves and other malformations obstruct normal cerebrospinal venous outflow, resulting in reflux flow which combines with the normal outflow to produce standing pressure waves in the internal jugular and other cerebrospinal veins. It is hypothesized that, if the cerebrospinal venous structure between the obstruction and the deep cerebral veins is sufficiently non-compliant, the standing wave will result in bidirectional flow in the fine cerebral veins. Bidirectional flow in the fine veins, over extended periods of time, will cause disorder in the veins' endothelial morphology, and ultimately, result in the disruption of the blood-brain barrier as observed in multiple sclerosis. This physics-based analysis demonstrates a positive correlation between clinically observed MS attributes with the predicted flow patterns and venous malformations that are based on fluid dynamics principles that include venous compliance influences. The physics-based approach used in this analysis provides new insights into MS pathologies based on predicted pressure and flow patterns.

Comparing the Superficial Vasculature of the Central Nervous System in Six Laboratory Animals: A Hypothesis About the Role of the "Circle of Willis".

We provide images of the entire central nervous system vasculature, and compare the anatomical findings in six different laboratory animals. A detailed understanding of the specific anatomy for each is important in the design of experimental modeling and for understanding the specific function of each target organ. Six different types of animals, the Korean wild mouse, C57BL/6J mouse, F344 rat, mongolian gerbil, Syrian hamsters, and guinea pigs, were included. To stain the blood vessels in each of the animals, Alcian blue reagent was used to perfuse each species. The bifurcation and anastomotic patterns of the anterior cerebral arteries differed in each species. The vascular supply to the olfactory nerve was visualized as a single artery supplying both olfactory nerves, and arteries supplying the lateral portion of the olfactory nerves originating from the olfactory bulb area. The posterior communicating arteries of the six animals demonstrated unique morphologies. The shape of the hypophyseal portal system varied by species. Most animals used in this study had a hexagonal Circle of Willis, except for the Korean wild mouse. Using this approach, we successfully mapped the brain vascular system in six different species of animals. This information and the images created can guide other researchers as they design research studies and create experimental models for new surgical procedures and approaches. Anat Rec, 2019. © 2019 Wiley Periodicals, Inc. Anat Rec, 302:2049-2061, 2019. © 2019 American Association for Anatomy.

Synchrotron radiation micro-tomography for high-resolution neurovascular network morphology investigation.

There has been increasing interest in using high-resolution micro-tomography to investigate the morphology of neurovascular networks in the central nervous system, which remain difficult to characterize due to their microscopic size as well as their delicate and complex 3D structure. Synchrotron radiation X-ray imaging, which has emerged as a cutting-edge imaging technology with a high spatial resolution, provides a novel platform for the non-destructive imaging of microvasculature networks at a sub-micrometre scale. When coupled with computed tomography, this technique allows the characterization of the 3D morphology of vasculature. The current review focuses on recent progress in developing synchrotron radiation methodology and its application in probing neurovascular networks, especially the pathological changes associated with vascular abnormalities in various model systems. Furthermore, this tool represents a powerful imaging modality that improves our understanding of the complex biological interactions between vascular function and neuronal activity in both physiological and pathological states.